Phase behaviour and physical properties of dimethyl ether (DME)/flue gas/water/heavy oil systems under reservoir conditions

Abstract

The application of a mixture of dimethyl ether (DME) and flue gas (i.e., CO2 + N2) is a promising method to recover heavy oil; however, the phase behaviour and physical properties of DME/flue gas/water/heavy oil systems are not well quantified. In this study, theoretical and experimental techniques are developed to determine phase behaviour and physical properties of the aforementioned systems at pressures ranging from 2 MPa to 20 MPa and temperatures spanning from 352.15 K to 433.15 K. Experimentally, eight constant composition expansion (CCE) tests are carried out to obtain new experimental data for the DME/flue gas/water/heavy oil systems for the first time. Theoretically, a thermodynamic model that incorporates the Peng-Robinson equation of state (PR EOS), a modified α function, the Péneloux volume-translation strategy, and the Huron-Vidal (HV) mixing rule has been modified to reproduce the measured phase equilibria data. The tuned binary interaction parameters (BIPs) are utilized in conjunction with the thermodynamic model to accurately predict saturation pressure (Psat) and swelling factors (SFs) with a root-mean-squared relative error (RMSRE) of 3.32% and 0.57%, respectively. Furthermore, the newly proposed model demonstrates its high accuracy in forecasting the oleic/vapor (LV) two-phase boundaries for N2/heavy oil systems and DME/CO2/heavy oil systems with an RMSRE of 1.93% and 2.77%, respectively. Similarly, the accuracies of the predicted aqueous/oleic/vapor (ALV) three-phase boundaries for N2/water/heavy oil systems and DME/flue gas/water/heavy oil systems are 2.85% and 3.47%, respectively. Water is found to increase the phase boundaries for DME/CO2/heavy oil systems but decrease those of N2/heavy oil systems and DME/flue gas/heavy oil systems. Additionally, as the concentration of N2 and/or CO2 in the mixture is increased, its Psat is increased.